Neural stimulation has been proposed as a therapy for a number of conditions. By way of example, neural stimulation may be delivered to modulate the autonomic system, which may be referred to as an autonomic modulation therapy (AMT). Examples of AMT include therapies for respiratory problems such as sleep disordered breathing, blood pressure control such as to treat hypertension, cardiac rhythm management, myocardial infarction and ischemia, heart failure (HF), and modulation of the cholinergic anti-inflammatory pathway. For example, therapies to treat epilepsy, depression, pain, migraines, eating disorders and obesity, and movement disorders may include stimulation of a vagus nerve.
Some neural targets are complex structures with different types of nerve fibers that may innervate different portions of the body. Indiscriminate stimulation of such complex structures may provide a desirable effect, but may also provide an undesired side effect. For example, the cervical vagus nerve is a combined nerve with different sized fibers. A recurrent laryngeal nerve branches off from the cervical vagus and innervates the muscle around the larynx. The vagus nerve continues to descend below the laryngeal nerve branch to innervate other portions of the body including the heart, lungs, liver, stomach, intestines, bladder and kidneys. Therapies, such as a heart failure therapy, that stimulate the cervical vagus nerve have been proposed. It may desirable to stimulate the cervical vagus nerve in a manner that activates the fibers that innervate the heart without activating some other fibers in the cervical vagus nerve so as to avoid unwanted physiologic responses to the stimulation.